CODEWITHSUNDEEP
javaswinguser-interfaceactionlistener
user1507910
user1507910

Reputation: 5

Exception in thread "main" java.lang.ClassCastException: hello cannot be cast to java.awt.event.ActionListener

it seems as though i have found a new problem in my code. my code has no (visible) errors, but i still get no frame. Please help

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class hello{
//Int's and things
static JButton Play = new JButton("<PLAY>");
static JFrame pane = new JFrame("CIrCUT 0.0.2");
static JLabel Title = new JLabel("CIrCUT");
static JLabel none = new JLabel(" ");
static JPanel panel = new JPanel(new GridLayout(10,10,10,10));
static JButton Options = new JButton("<OPTIONS>");
static JPanel panel2 = new JPanel(new GridLayout(10,10,10,10));
static String b[]  = new String[3];
static int panelLoct =1;
JComboBox optionlist = new JComboBox();


    void initialize(){
    b[0] = "High";
    b[1] = "Medium";
    b[2] = "Low";

    //title
    pane.setTitle("CIrCUT 0.0.2");
    //drop down

    optionlist .setModel(new DefaultComboBoxModel(new String[] {"Option", "High", "Medium",  "Low"}));
    optionlist.setSelectedIndex(3);
    optionlist.addActionListener((ActionListener) this);
    //other pane-related things
    if(panelLoct==1){
    pane.setLayout(new GridLayout(10,10));
    panel.setMaximumSize(new Dimension(500,500));
    pane.setSize(500,500);
    pane.setMaximumSize(new Dimension(500,500));
    panel.add(Title);
    panel.add(none);
    panel.add(Play);
    panel.add(Options);
    panel2.add(optionlist);
    Play.setSize(new Dimension(500,450));
    pane.setLocation(500,50);
    pane.setBackground(Color.lightGray);
    pane.setContentPane(panel);
    pane.pack();
    pane.setMinimumSize(new Dimension(500,500));
    pane.setContentPane(panel);
    OptionButtonHandler cbHandler = new OptionButtonHandler();
    Options.addActionListener(cbHandler);
    pane.setVisible(true);
    }
}
    public void windowClosing(WindowEvent e)
    {
    System.exit(0);
    }
     private static class OptionButtonHandler implements ActionListener

         {
             public void actionPerformed(ActionEvent e){
                 pane.remove(panel);
                 pane.add(panel2);
             }
         }
     public void actionPerformed(ActionEvent e) {
            JComboBox cb = (JComboBox)e.getSource();
            cb.getSelectedItem();
     }

public static void main(String args[])
{
    hello a = new hello();
    a.initialize();
}
}

any help at all would be much appreciated. here is the error i get when i try to run it

Exception in thread "main" java.lang.ClassCastException: hello cannot be cast to java.awt.event.ActionListener
    at hello.initialize(hello.java:39)
    at hello.main(hello.java:83)

It is probably a novice mistake, but could find nothing on how to solve it.

Upvotes: 0

Views: 8946

Answers (3)

Ahmet Karakaya
Ahmet Karakaya

Reputation: 10139

You have to implement ActionListener.

public class Hello implements ActionListener{ 

}

Upvotes: 0

Yann Ramin
Yann Ramin

Reputation: 33187

    optionlist.addActionListener((ActionListener) this);

Just because you will something doesn't mean it is possible. In this case, hello is not an ActionListener, so this will fail.

If you find yourself casting, you likely have a problem.

Upvotes: 2

Jon Skeet
Jon Skeet

Reputation: 1500873

Your program does have a visible error, precisely where it's failing:

optionlist.addActionListener((ActionListener) this);

this is a reference to an instance of hello. The hello class doesn't implement ActionListener - so how would you expect that cast to succeed?

The only implementation of ActionListener you've given is OptionButtonHandler. Perhaps you meant:

optionlist.addActionListener(new OptionButtonHandler());

?

Upvotes: 3

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